Predictive model for drinking water treatment technology design - the efficiency of arsenic removal by in-situ formed ferric-hydroxide

Abstract

Coagulation by ferric-salt is a widely used technique for arsenic removal. Jar tests with synthetic water were conducted in order to investigate the combined effect of the raw water characteristics on the removal efficiency of in-situ formed ferric-hydroxide. Multiple linear regression analysis was carried to establish a robust model, which is able to estimate the residual arsenic concentration provided that the raw water contained 50-60 μg/L initial arsenic concentration. The estimation was based on the following variables: PO₄-P concentration, final pH, SiO₂ concentration and Fe³⁺ dose. The major factors influencing efficacy were the silicate concentration and applied coagulant dosage. The model was verified by data from 24 additional experiments, and the predicted and measured residual arsenic concentrations showed good agreement (R² = 0.87).